In the metal industry, it has been common for a period of time to use disposable thermocouples for measuring the temperature of a molten bath and to use disposable thermocouples as part of a phase change device. Such phase change devices are utilized, for example, when detecting the thermal arrest temperature of a molten metal.
Examples of prior art related to disposable thermocouples for use in connection with measuring the temperature of a molten bath include U.S. Pat. Nos. 3,011,005; 3,048,642; 3,493,439; and 3,531,331. Examples of prior art disclosing phase change cups which include a thermocouple are U.S. Pat. Nos. 3,267,732, 3,611,808 and 3,946,594.
Difficulties have been noted, especially in connection with phase change cups, with respect to the appreciable length of time during which the thermocouple hot junction is subjected to considerable stresses. It is often noted that temperature measurements are not perfectly reproducible from one device to the next. It is believed that the discrepancy is due mainly to the manner of forming the thermocouple hot junction on the one hand, and due to the influence of carbonization of resins in the refractory cup which becomes slightly electrically conductive. The present invention overcomes each of these objectionable features.